1. Field of the Invention
The invention concerns disc brake pad retractors. More specifically a disc brake pad retractor for urging a brake pad away from the brake rotor or disc when the brakes are not being applied is provided.
2. Description of the Prior Art
Disc brake systems are widely used in the automobile and truck industry for controlling the velocity of motor vehicles. The operation of the disc brake system is well known. When the brakes are applied a hydraulic cylinder is urged toward the rotating brake rotor. Friction pads are thus pushed against both sides of the rotor and the clamping force of the pads on the rotor will arrest the rotor motion and stop the vehicle.
When the brake pads are released after being applied, the brake piston will not automatically back away from the applied position unless it is spring loaded to back off. Conventional disc brakes are often subject to undesirable drag of the disengaged pads on the rotors. The drag causes power losses, a shortening of the service life of the pad and possible overheating of the brake components and wheel bearings. Drag is caused by brake pads being constantly urged against the disc at nominal pressure even after release of the application pressure. This could be caused by the oil seal of the brake piston preventing retraction of the piston to its original position as the piston was forced out under application pressure for a distance corresponding to an amount equal to caliper housing elastic deflection. New disc brake systems and specifically the brake rotors of such systems are often machined with a small amount of "run out" that is used to push the unenergized pad and piston assembly away from the brake rotor. This "run out" method is not always adequate to urge the pads away from the rotor as the "run out" of the rotor will quickly become negligable as the brake is used.
Another method of disc brake pad retraction depends on the seals of the brake piston to resiliently deform when the brake is applied. Upon release of the brake the seals will return to their original shape and retract the brake piston into the piston bore. The pads however, will remain in light contact with the rotor unless they are directly affixed to the pistons. Other mechanical retractors are known in the prior art as well. Return springs incorporated into the piston are known. The problem with this type of retractor is that unless the brake pads are fastened directly to the brake piston retracting mechanism the piston will only release pressure behind the pads but won't necessarily move the pads away from the rotor. Attaching the piston to the pads solves the problem, but makes pad replacement difficult and requires the use of specially manufactured brake pads resulting in increased cost and manufacturing difficulties.
Ratcheting type brake adjusters are also known but these are generally used to enable the stroke of the piston to be controlled so that the piston need not be moved through full stroke every time the brake is applied. This type of device is able to adjust only in incremental amounts equivalent to the degrees allowed by each ratchet tooth. The instant invention, however, is adjusted upon each brake application and also serves to urge at least one pad away from the disc.
The apparatus set forth in this invention seeks to provide a brake pad retractor that will urge a brake pad of a disc brake assembly away from the brake rotor after the brake has been released.